In many situations where fluorescent lighting is used, it is desirable to provide plural levels of lighting. A typical example involves full level lighting during the day to provide sufficient light for work or task activities and some minimum level of lighting during the night after normal working hours. The night level provides sufficient light for security purposes and the like while saving energy with reduced lighting. Hallways in buildings provide an excellent application for such plural level lighting.
The most common prior art approach to providing plural levels of lighting involves wiring groups of fixtures into distinct circuits, with each circuit controlled by its own switch means. To obtain the desired level of lighting, the respective switch means are operated to energize and de-energize the desired circuits Because groups of fixtures are controlled, the fluorescent light tubes in any given fixture are either all on or all off. Other prior art approaches to providing plural levels of lighting in fluorescent lighting installations have involved complex control apparatus including a central controller means for controlling lamps in multiple zones and requiring extensive low voltage control wiring The prior art approaches of which I am aware are lacking in economy, simplicity and flexibility.
The objective of the present invention is to provide a selectable plural light level capability in fluorescent lighting installations in a manner that will achieve the goals of economy, simplicity and flexibility.